Parts of a CircleVersión en línea This matching activity reviews key terms for parts of a circle. por Stephanie Cintron 1 Parts of a Circle Related to the Interior 2 Parts of a Circle Related to the Exterior 3 Involving More than One Circle 4 Key Formulas Center Radius Diameter Chord Area Secant Tangent Point of Tangency Circumference Concentric Circles Tangent Circles Common Tangent Arc Length of a Circle Area of a Sector Area of Circle Circumference of Circle